The present disclosure relates generally to the field of nonvolatile memory devices, and more specifically to programming a magnetic element of a magnetic random access memory (MRAM) device.
MRAM is a nonvolatile memory technology that uses magnetization to represent stored data. MRAMs are beneficial in that they retain stored data in the absence of electricity. Generally, MRAM structure includes a plurality of magnetic cells in an array. Each cell generally represents one bit of data. Each cell includes at least one magnetic element. A magnetic element may include two ferromagnetic “plates” (e.g. layers upon a semiconductor substrate) each which has a magnetization direction (orientation of magnetic moments or direction of a magnetization vector) associated with it. The two ferromagnetic plates are separated by a thin non-magnetic layer. One of the ferromagnetic plates, the free layer (also known as a storage layer) has a magnetization vector that is free to rotate. The magnetization vector of other ferromagnetic plate, the pinned layer (also known as a reference layer) has a set, or “pinned” direction. In programming the magnetic element, typically, a “0” is written to a magnetic element by aligning the magnetization vectors of the ferromagnetic plates in a parallel manner and a “1” is written to a magnetic element by aligning the magnetization vectors of the ferromagnetic plates in an antiparallel manner. The magnetic element may be read by determining the resistance of the element. A magnetic element with parallel magnetization vectors of its ferromagnetic plates has a low resistance state. A magnetic element with antiparallel magnetization vectors of its ferromagnetic plates has a high resistance state.
The direction of magnetization of the free layer of the magnetic element may switched by introducing a current (a write current) to the magnetic element. One conventional manner of switching the magnetization direction of the free layer is spin torque transfer (STT), also known as spin transfer switching or spin-transfer effect or current induced magnetization switching (CIMS). STT is based on the idea that when a spin-polarized current is applied to a free layer the electrons may get repolarized because of the orientation of the magnetic moments of the free layer. The repolarizing of the electrons leads to the free layer experiencing a torque associated with the changed in the angular momentum of the electrons as they get repolarized. As a result, if the current density is high enough, this torque has enough energy to switch the direction of the magnetization vector of the free layer. STT has many advantages as known in the art, for example, smaller bit size, lower number of process steps as compared to other writing techniques, scalability for large arrays, and requiring a lower writing current. However, there is also a disadvantage in that STT requires a bidirectional current source. More specifically, switching from an antiparallel to a parallel configuration of the magnetization of a free layer and a pinned layer takes a current from a first direction while switching from a parallel configuration to an antiparallel direction takes a current from a second direction. In order to facilitate this bidirectional current, a current switch is necessary on the periphery of the array of cells including the magnetic elements. The presence of this switch increases the costs MRAM devices in terms of occupying device area, additional fabrication processes, complexity, and other costs known in the art.
As such, an improved method for programming a magnetic element and a memory device providing for improved programming of a magnetic element included in the device is desired.